The invention relates to a filing system for managing recording and retrieving of information files on a record carrier of a rewritable type, which system comprises means for generating non-file and file items comprising management information and means for assigning areas on the record carrier for recording the items, the management information comprising references indicative for the areas, said items comprising at least one item of a first type to be recorded on a predetermined area and items of a second type to be recorded on variable areas
Such a filing system is described in ISO 9660 `Information Processing--Volume and file structure of CD-ROM for information interchange, corrected edition, September 1988`. In this document a filing system for recording and retrieving files on/from a record carrier is defined, which is used for the well known CD-ROM. The file management information is structured in non-file items and file items. The non-file items comprise a Primary Volume Descriptor (PVD), Supplementary Volume Descriptor(s) (SVD), and a Path Table (PT), which contains the addresses of all directory files. The PVD must be on a fixed location on the record carrier, such that a recording system is always able to locate the basic information about the logical structure of the stored information. File items may comprise system information files and directory files. The directory files comprise the addresses of individual files and other directories in so called Directory Records (DREC); the directories forming a hierarchical system starting at a root directory (RD). The PVD and the PT comprise the address of the RD.
For compatibility reasons a similar filing system is needed for recordable and/or erasable record carriers, such as CD-E (Erasable). However the CD-E is based on phase change technology, which allows only a limited number of overwrites (e.g. 1000 times). Therefore the operational life of such a record carrier is limited. A problem may arise relatively early in areas which are frequently overwritten, especially if the area has a fixed location, such as the PVD.
If ISO 9660 was followed explicitly, then the PVD would be rewritten whenever:
1. The root directory address changes. This will occur whenever either a DREC of a file or directory is modified, added to or deleted from the root directory of the volume. PA1 2. The path table is relocated. This will occur whenever a new directory is added anywhere on the volume which causes the path table to grow beyond its currently allocated space. This can also occur on CD-E when the write or the verify after write suggest that the location is either bad or risky. PA1 3. The path table changes size. Whenever a new directory, anywhere on the volume, is added or whenever an old directory, anywhere on the volume, is deleted, the path table changes size. PA1 1. A directory anywhere on the volume is added. PA1 2. A directory anywhere on the volume is deleted. PA1 3. A directory anywhere on the volume is relocated. PA1 4. The name of a directory anywhere on the volume is changed.
Note: the above concerns apply equally to the SVD.
The path table PT is the second most likely item to require frequent updates. If ISO 9660 was followed explicitly, then the path table would be rewritten whenever.